Trained at the Nuri hospital in Damascus and later chief physician at the Al-Mansuri hospital in Cairo, Ibn al-Nafis wrote at age 29 the Sharh Tashrih al-Qanun, refuting the Galenic doctrine of invisible pores in the interventricular septum and proposing instead pulmonary circulation, also predicting perceptible passages between pulmonary artery and vein — later identified as capillaries by Malpighi. The manuscript had no documented influence in Europe until its 1924 rediscovery in Berlin's Prussian State Library.